Hydraulic shock absorber



Aug. 27, 1940.

J. MERCIER HYDRAULIC SHOCK ABSORBER Filed Det?. 8, 1937 l \\\\\\\\\\\\\\\\\\\\\\\\r' Y -"Tan-n Merc lef 'INVENTQQ Patented Aug. 27, 1940 UNITED STATES PATENT OFFICE Application December s, 1937, serial No. 178,693 In France September 27, 1937 Claims.

The present invention has for its object a hydraulic shock-absorber, of the type comprising two elements slidably mounted one within the other, said shock-absorber being chiefly adapted for use on landing gear for airplanes. The said shock-absorber consists principally of two parts containing oil or another liquid, and one of which is slidable in the other after the manner of a cylinder `and a piston. It is characterized in that 10 it provides for a diierential operation of the shock-absorber according to the rate o f the relative movements of the two slidable elements, and in that the partition separating the two chambers which are formed by the two slidable l5 elements and which are lled with liquid, comprises three circuits of communication, one of which is always open, has a relatively small section, and only allows slow movements of the said slidable elements in either direction, while the other two circuits have a relatively large section, thus affording a great output of the uid, these latter circuits beingprovided with check-valves or poppet-valves having calibrated reaction springs. One of the said valves comprises an additional closing member. The said springs have different forces, and are adapted to close the two circuits of large output. They are mounted on the wall separating the two chambers which are formed by the said slidable parts.

In order to insure non-leaking conditions for the said apparatus, use may be made of suitable packing or of a stuffing-box located between the two slidable parts.

On the other hand, the said parts may be surrounded by an elastic ball-shaped device which is secured at one end to one of the said slidable parts and at the other end to the second slidable part. The said device comprises an air chamber 40 the volume of which is reduced when one of the parts is driven into the other, and is expanded when these parts are separated. Thus the device will serve for non-leaking purposes, and will also act as an elastic reaction device which 4will have 45 a tendency to bring the two slidable parts into a relative mean position.

This elastic reaction device may also consist of springs of a curved shape or of the elliptical 50 type, which surround the two aforesaid parts and are secured a-t their ends to the two respective parts.

By the use, as' an elastic reaction device, of a bal1-shaped member forming an air chamber, or

55 of spring strips which connect the two slidable vice or spring strips, are employed in order to prevent the relative rotation of the twoparts, it is possible to reduce the angular stresses exerted upon the ball-shaped device or the springs, by 15 connecting the wheel axis or a member carrying this axis, to a. xed point -of the airplane by pivot joints and by means of an extensible strut.

It is further possible to prevent such relative angular movements of the two slidable parts, by 20 means of a bar which passes through lugs provided upon collars or the like which are secured to the two parts.

Further features of the invention will be disclosed in the following description.

In the accompanying drawing, which are given by way of example:

Fig. 1 shows a shock-absorber in conformity with the invention.

Fig. 2 shows a shock-absorber mounted on the 30 landing gear of an'aeroplane and comprising an elastic ball-shaped device or spring plates forming an elastic device and preventing the two slidable parts of the shock-absorber from turning with reference to each other. 35

Fig. 3 shows landing gear of the type represented in Fig. 2, in whichv a forked bracket or like part supporting the axis of the wheel is pivoted to an extensible strut which is pivotally mounted at a x'ed point on the airplane body.

Fig. 4 shows another embodiment.

In the embodiment shown in Fig. 1, the shockabsorber consists of two tubular parts I and 2, Apart 2 being slidable in part4 I. The space or chamber between these two parts is filled with a liquid, and a sealing joint between these two parts is formed by means of a packing member 3 `or 'thelike. The bottom wall which separates the inner part of element 2 from the inner part of element l is provided with three orifices 4, 5 50 and 6. Orice 5, which has a small diameter, is always open. Orifice 4, which has a relatively large diameter, is normally closed by al valve 'I controlled by a calibrated spring 8 which bears at the other end upon a boss 9 situated in part `455 material.

2. lThe said valve can only open when the pressure in part I increases to a dangerous value. The third orifice 6, the diameter of which is also relatively large, is provided with a'double valve IU-II subjected to the action of a relatively weak spring I2 which bears upon a boss situated within part 2. The said spring tends lto close orice 6 by means of part I0 of the double valvejIIl-II.

The operation of this shock-absorber is as follows: When part 2 rises or descends slowly, the

resistance of the shock-absorber is relatively' great, due to the fact that the liquid in order to balance the pressures in I and 2 can only pass' through the small orifice 5, orifices and 5 being closed by their respective valves `I and I0. On the contrary, when part 2 is lowered atan average speed, valve I0 is driven back against its spring I2 under the eiects of the pressure exerted upon part II, and thus the uid can readily pass through the large orifice 5.

For this kind of displacements, the shockabsorber will operate smoothly. On the contrary, if part 2 descends abruptly, the sections of orifices 5 and 6 will not be sumcient to balance with a sulcient speed the pressures in the two tubular parts. The pressure in part I will considerably increase, thus closing valve I I against the weak spring I2. At this moment, if the chambers in the two parts were only connected by the narrow orifice 5, the damping would take place in a very abrupt way. It will be noted that in this'case, (the balancing being only possible through the small oriiice 5), the pressure in part I may reach values which are dangerous for the apparatus. For this reason, the force of spring 8 which normally closes the valve l, is so chosen that this valve will open when the pressure prevailing above it rises to a dangerous point. In these conditions, the large orice 4 will open when the pressure reaches this limit, and the balancing of the pressures will take place through the oriilces 4 and 5.

When part 2 rises in part I, the resistance of the shock-absorber is still rather high, as the two orices 4 and 6 remain closed, and the balancing can only take place through orice 5.

Fig. 2 shows a modification, in which the shock absorber of the above-mentioned type is mounted on the landing gear of an airplane. In this iigure, the shock-absorber is represented in an entirely diagrammatic manner by a cylinder I and a piston 2. The cylinder is connected at the top to Va fixed point` on the airplane; the rod I5 of the piston 2 is secured toa forked bracket or like4 member I5 carrying the axis of the wheel II of the landing gear. Obviously, the shock-absorber I-'-2 may beconstructed in practice in the forni of two tubular parts I and 2 which are mutual-lyA slidable and have all the features (valves and orifices) shown in Fig. l.

In order to obtainnon-leaking conditions be- `tween the parts I and 2, as well as an elastic return to the idle position, the two parts I and 2 are connected, for instance, to an elastic ballshaped device I8, consisting of rubber or like The said device is connected at I9 -and 2D, in a non-leaking manner, to the two slidable parts, respectively. `This tight connection for the elastic device is preferably made by vulcanizing the rubber on the metallic surface 'of the two l parts I and 2, and if necessary, in order to give greater strength to this connection, between this metallic surface and an outer collarsuch as IIB, ne' which is acted upon the rubber at this pointr VPatent is:

. ing slidable within the other and forming a de- As the ball-shaped device is filled with air, it will havel a tendency, after any deformation caused by the relative movements ofthe parts I and 2, to restore these latter to the mean position.

' The lball-shaped device I8 may consist of a 5 sufliciently strong material, such as rubber. provided with threads having a diagonal weave (crossed cords), or the like, and in this case it can also serve to prevent the two parts I and 2, and hence the Wheel I I and the airplane body, from turning with reference to each other. This willobviate theuse' lof the means hitherto employed for this purpose, such as grooves or keys which serve to secure the parts I and 2 together in the angular direction.

The ball-shaped device may also be replaced by spring strips. The' said springs may be lo cated between the two parts I and 2 and may be pivoted, respectively at I9 and v2l), to these parts. In this construction, an elastic return is also provided. At the same time, the said springs may serve to prevent the parts I and 2 from turning with reference to each other.

It is evident that the springs will not serve for non-leaking purposes, and thus aspeci'al joint must be provided between thepartsl and 2, which may resemble the one shown at 3 in Fig. 1.

Fig. 3, which is in principle identical with Fig. i 2 shows another method for connecting the two parts. 'together 4in the angular direction. This 30 method consists in connecting the member I 6 carrying the axis of the wheel, or the axis itself, to an extensible strut, consisting for example of a telescoping system 22-2l which in the present case is pivoted at one end to the member IBat 23 and at the other end to the airplane body at 25. The-said extensible strut could obviously be used in combination with a ball-shaped device or springs I8, as shown in Fig. 2, and herein it will serve to reduce the torsion stress exerted 40 upon the elastic parts I8.

Fig. 4 shows another construction, in whichhe two parts I and 2 are connected together in the angular direction by a rod 29 passing through superposed lugs, one set, lugs 26, being mounted on part I, and the other set 28, on part 2, or again, as shown in Fig. 4, on the body of the airplane or the spar 21.

Obviously, the invention is not `limited to the forms of construction herein described and represented, which are givenvsolely by wayv of example. V

For instance, instead of using the orifices 4, 5, 6 and their accessories upon a movable separating wall, as shown in Fig. 1, they can be used equally well on a4 xed wall, as shown in Fig. 2, thus forming a second chamber in the cylinder.

Having now described my invention, 'what I claim as new and desire to secure by.Letters 1. A hydraulic shock-absorbing device comprising two members forming a piston and cylinder like arrangement, one of said members bevalve means, one of said valve means being of the double type and provided with an additional closing part, said reaction elements being of different force, adapted to close said two latter circuits and mounted on said separating means.

2. A hydraulic shock absorbing device compris'- ing two members forming a piston and cylinder like arrangement, one of said members being slidable within the other and forming a deform- A able chamber, which is iilled with a suitable fluid, separating means in said chamber creating two compartments, channel means in said separating means constitutingthree circuitsof communication between said compartments, one of said channel means being `always open and having a relatively small cross-section so as to aii'ord only slow movements of the two slidable parts in both directions, the other two channel means having relatively large cross-sections, thus allowing the iiuid to now at a considerable rate, valve means in said two latter channels, and, preferablyA calibrated reaction elements acting upon said valve means, one of said valve means 'being of the double type and provided with an additional closing part, said reaction elements being `of different force, adapted to close said two latter channels and mountedon said separating means.

3. A shock-absorber as claimed, in claim 1, wherein said valve means consist of two checkvalves and wherein the force of the reaction element, such as a spring, acting upon the double valve is less than the force of the reaction element acting upon the other valve.

4. A shock-absorber as claimed in claim 1, wherein said double valve means consists of two obturating elements located on both sides of said separating means and of a rod `connecting said elements and slidably located in said separating means.

5. A hydraulic shock absorbing device comprising two members forming a piston and cylinder like arrangement, one of said members being slidable within the other and forming a deformable chamber which is filled with a suitable uid, separating means in said chamber, creating two compartments, three circuits of communication between said compartments provided in said separating l means, one of said circuits being always open and having a relatively small crosssection so as to afford only slow movements of the two slidable parts in both directions, the other two circuits having relatively large cross-sections, 4

thus allowing the uid to flow at a considerable rate, valve means in said two latter circuits, and preferably calibrated reaction elements acting upon said valve means, one ofA said valve means consisting of two obturating elements located on l both sides of said separating means, and of a rod connecting said elements and slidably located in said separating means, the force of the reaction element, such as a, spring, acting upon the double valve being less than the force of the reaction element acting upon the other valve.

6. A shock absorbing device comprising two members forming a piston and cylinder like arrangement, one of said members being slid'- able within the other and forming a deformable chamber, which is lled with a suitable uid, separating means in said chamber, creating two compartments,I three circuits of communication in said separating means between said compartments, one of said circuits being always open and parts in both directions, the other two circuits having relatively largecross-sections, thus allowging the iluid to flow ata considerable rate, valve means in said two latter circuits, and'preferably calibrated reaction elements actingl upon said valve means, one of said valve means being of the double type and provided with an additional closing part, said reaction elements being of different force, adapted to closesaid two latter circuits and mounted on said separating means, the reaction element, such as a spring, which acts upon said double Valve means being adapted to close the corresponding circuit in the idle position and during the slow deformation of the shock-absorber, -andl opening the said circuit against the'action of the said spring'in the case of movements of compression at average speed, but closing it again in the case of sudden compression.` l '7.` A shock absorber according to claim 6, wherein said second reaction means is adapted to close the corresponding circuit for large output when in the idle position and during the extension, and also during all the movements of compression of the shock-absorber which will not cause `any dangerous increase of the pressure in the cylinder-like member.

8. A shock-absorber according to claim 1 wherein said two slidable members consist of hollow bodies, the separating means pertaining to the piston-like member.-

9. A shock-absorber according to claim 1, wherein one of said members consists of a `hollow body, said separating means forming the two compartments being located in this body.

l0. A shock-absorbing device according to claim 6 wherein said two slidable members conand creating two compartments, channel means in said partition means forming three distinct circuits causing said compartments to communil cate, one of said circuits being always open and having a relatively small cross-section soas to afford only slow movements of the two slidable parts in both directions, the other two circuits having relatively large cross-sections, thus allowing the uid to flow at a considerable rate, valve v means in said two latter circuits, preferably calibrated, reaction elements acting upon said valves,

means, one of said valve means being of the double type and provided with an additional closing part, ysaid reaction elements being of different force, adapted to close said two latter circuits and .mounted on said partition means; and,

further an elastic part mounted between said slidable members and tightly secured to each of these members, thus forming an elastic reaction device.4 i Y 12. A shock-absorber according toclaim 11 wherein said elastic part consists of a balloon of rubberized fabric with crossed cords and yis secured to the metallic surfaces of the slidable "members by vulcanizing processes, and further metallic rings preferably provided on the rubber at the securing places in order to hold the rubber between metallic surfaces.

13. A shock-absorber according to claim 11 wherein said elastic part consists of a balloon of rubberized fabric with diagonal cords and is` secured to the metallic surfaces of the slidable members by vulcanizing processes, and further.

aircraft body and the other to the landing gearv support, and providing a working chamber and a separate chamber, both containing damping fluid, means providing three passages between the chambers, one passage free but narrow and adapted to afford only slow reciprocations of the gear, the second substantially larger so as to moderately damp average speed movements, and the third likewise substantially larger, double valve means for controlling the second passage and including a normally closed non-retum valve loaded to open at a moderate pressure and a normally open check-valve loaded to be closed by a rush of iluid, and a relief valve-for controlling the third passage, loaded to open when the iluid pressure nears a dangerousvalue, thereby to provide for a two-stage flow for a moderatedamping at running and smooth landings, a further two-stage flow for a strong damping at rough landings, and a restricted ow for moderately damping the return strokes or rebounds of the gear.

JEAN MERCER. 

